Various pressure sensitive encapsulated toner particles are known which have a core portion and an enveloping shell portion. For example, U.S. Pat. Nos. 4,590,142; 4,626,490 and 4,535,049 teach toner particles having a waxy core and a polymeric shell. U.S. Pat. No. 3,788,994 teaches toner powders having a core of cold flowable adhesive material and a polymeric shell. U.S. Pat. No. 4,254,201 teaches granule clusters wherein each granule has a core of pressure-sensitive adhesive. U.S. Pat. No. 4,533,617 teaches cores of binder resin and colorant coated with a thermoplastic resin shell. Japanese published Patent Application J52113-74C teaches a microcapsule toner having a soft material core that is coated with a polymer layer, and then with a hard resin layer containing soft polymer and colorant. All of such publications teach the use of such toner particles for pressure-fixing deposited toners in electrophotography, but they provide no teaching of using such particles for toned image transfer purposes.
Various patents teach techniques for accomplishing transfer of toner particle developed photoelectrostatic images from a photoconductor surface to a receiver surface using pressure. For example, U.S. Pat. Nos. 3,627,523 and 3,843,381 uses a transfer roll applied with pressure to a receiver sheet pressed against a toned image on a photoconductor to transfer the image followed by toner fixing by heat fusion on the receiver sheet. U.S. Pat. No. 3,442,645 uses applied pressure surface on a charged dielectric sheet positioned on the outside surface of a receiver sheet that is placed against a toner image on a photoconductor to transfer the toned image from to the receiver sheet. U.S. Pat. No. 4,380,385 teaches transfer of a toner powder image from a rotatable drum surface to a receiver sheet by a pressure roller whose axis is inclined relative to the drum axis to achieve a sliding action. Japanese Patent Publication No. J5503071 teaches transferring a toner powder image from a carrier to paper with a pressure roller whose circumferential surface is coated with a smooth polymer. These publications, however, do not teach using pressure sensitive encapsulated toners for toned image transfer purposes.
Toner particles comprised of a pigmented core polymer coated with fine-grained polymer particles are provided by U.S. Pat. Nos. 4,794,065 and 4,833,060 and PCT Application No. W088/07225. However, the product toner particles do not appear to be particularly pressure sensitive and no use of such toner particles for the pressure transfer of toned images is taught.
So far as is now known, no one has heretofore utilized highly pressure sensitive, encapsulated toner particles with uniform characteristics for toned image transfer from a photoconductor to a receiver member after which the so transferred toned imaged is heat fused to the receiver sheet. Also, so far as now known, no one has heretofore provided a class of highly pressure sensitive encapsulated toner particles with uniform characteristics that is reasonably storage stable, has good toner flow and is suitable for full and accurate transfer of a toned image from a photoconductor surface to a receiver surface.